A conventional clamp for disengaging the inlet or exhaust valve from an engine is shown in FIG. 4, and includes an arcuated frame 61 having a first end with a disk 62 connected thereto which has a slit 621 defined therethrough, and a second end having a lever 70 pivotally connected thereto. A plate 71 is pivotally connected to the lever 70 and the second end of the frame 61. Two links 72 have their two respective first ends pivotally connected to the plate 71 in parallel with each other. Two elongated rods 63 are pivotally connected to the frame 61 near the second end of the frame 61 and the two respective second ends of the two links 72 are pivotally connected to one of the two elongated boards 63. A U-shaped bracket 64 is connected to two distal ends of the elongated rods 63, and a rack 65 movably extends through the bracket 64. A stop 67 is pivotally connected to the bracket 64 so as to engage with the teeth 651 of the rack 65 and a driving member 69 is rotatably received in the bracket 64 and is driven by a knob 68 mounted outside of the bracket 64. The rack 65 has a ring member 66 attached to the end thereof facing to the disk 62.
Referring to FIGS. 5 and 6, a vehicle cylinder head 50 has a plurality of combustion chamber ends 51 (FIG. 6) and each of the combustion chamber ends 51 has two inlet valves 52 and two exhaust valves 53. Taking the exhaust valve 53 as an example to describe the conventional clamp, the exhaust valve 53 includes a stem 532 extending through the head casing and a spring 55 is mounted to the stem 532 that extends from the interior of the combustion chamber 51 with an end member 56 and a stop member 57 respectively mounted to the distal end of the stem 532. The spring 55 has one end thereof mounted to the end member 56 and the other end contacting the outer periphery of the cylinder head 50. The stop member 57 is used to hold the spring 55 on the stem 532. The other end of the stem 532 has a valve disk 531 which has an annular inclined surface to engage with a seat defining the opening in the engine casing.
When operating the clamp, the disk 62 is mounted over the stem 532 which is received in the slit 621, and the disk 62 is located between the end member 56 and the stop member 57. The valve disk 531 is pressed by the ring member 66 of the rack 65 by pushing the lever 70 downwardly to let the links 72 push the two elongated rods 63 together with the bracket 64 toward the cylinder head 50. The knob 68 is then rotated to drive the driving member 69 to move the rack 65 toward the valve disk 531 till the spring 55 is compressed and the end member 56 is moved away from the stop member 57. The stop 67 has the function as a ratchet pawl so that when the rack 65 is moved toward the valve disk 531, the stop 67 will not impede the movement of the rack 65 and prevents the rack 65 from moving back. The stop member 57 then can be removed from the stem 532 by a proper tool so that the stem 532 can be pulled from the cylinder head 50.
The conventional clamp is deemed to include too many parts. Furthermore, it is difficult to compress the spring 55 simply by rotating the knob 68, especially when the operator's hands are covered with grease or oil. The torque output from the driving member 69 is limited because its size is small.
The present invention intends to provide a clamp for disengaging the inlet or exhaust valve from the engine, wherein the clamp has a simple structure and is easily to operate so that the disadvantage of the conventional clamp mentioned above can be obviated.